Thermal Grease

[Garey Barrell]

J. Forster wrote:

>Garey Barrell wrote:
>
>
>
>>Jerry -
>>
>>There are at least two types that I am aware of.
>>
>>The "old" style was clear silicone grease.
>>
>>The "new" style is white silicone grease loaded with beryllium oxide.
>>
>>
>
>
>
>>(snip)
>>
>>
>
>
>
>>By the way, beryllium oxide DUST is considered very toxic if inhaled, so
>>I guess you wouldn't want to eat the stuff!
>>
>>
>
>I don't think that the white colored silicone grease contains beryllium oxide, but
>has something like aluminum or zinc oxide instead. The reason is toxicity of
>beryllium compounds.
>
>There are ceramics made of beryllia (heat sink washers and parts of TWT tubes)
>used in electronics, but not the greases. See:
>
>http://www.wakefield.com/pdf/MSDS_120.pdf
>
>for example.
>
>-John
>
>

John -

Yes, you are correct.

Eimac made some tubes (8873?) with beryllium "thermal" links on the
anodes for heat sinking rather than fins for forced air cooling.   They
were used in a Heath linear amplifier, and of course have since been
discontinued.  Probably because the lawyers got involved!  :-)

We used the white grease from Wakefield in the 60's at NASA.  Guess we
could have rubbed it on our noses for sun protection at the beach!

73, Garey - K4OAH
Atlanta

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